// Source : https://leetcode-cn.com/problems/remove-linked-list-elements/
// Author : jkbs487
// Date   : 2021-06-05

/***************************************************************************************************** 
 *
 * Given the head of a linked list and an integer val, remove all the nodes of the linked list that 
 * has Node.val == val, and return the new head.
 * 
 * Example 1:
 * 
 * Input: head = [1,2,6,3,4,5,6], val = 6
 * Output: [1,2,3,4,5]
 * 
 * Example 2:
 * 
 * Input: head = [], val = 1
 * Output: []
 * 
 * Example 3:
 * 
 * Input: head = [7,7,7,7], val = 7
 * Output: []
 * 
 * Constraints:
 * 
 * 	The number of nodes in the list is in the range [0, 104].
 * 	1 <= Node.val <= 50
 * 	0 <= k <= 50
 ******************************************************************************************************/

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* removeElements(ListNode* head, int val) {
        while (head && head->val == val) {
            head = head->next;
        }
        ListNode* cur = head;
        while (cur) {
            if (cur->next && cur->next->val == val) {
                cur->next = cur->next->next;
            }
            else cur = cur->next;
        }
        return head;
    }
};
